Portable communication devices, such as selective call receivers, have relatively small visual displays in order to maintain the diminutive size of the portable device. Typically, selective call receivers are capable of receiving messages containing many more alphanumeric characters than the maximum number of alphanumeric characters that can be simultaneously displayed on a display device. As a result, only a portion of long messages can be displayed at one time, and the long message must process, or be scrolled, across the display, such as, for example, from right-to-left. The procession of textual material across a relatively small display device produces several disadvantages, one of which is that portions of the text disappear from view after having been displayed for a very short time; furthermore, such portions could contain the most important part of the message, such as the part having a telephone number or the part having a long, uncommon word, such as a person's surname. While a typical user can recognize a telephone number or a long surname as being what they are, a typical user cannot easily memorize the telephone number or the exact spelling of a person's surname. Prior art selective call receivers have provisions for retrieving from memory those portions of a message that are no longer being displayed; however, such known provisions require a user to first depress buttons or otherwise enter commands, and then disadvantageously require the user to manually scroll through the message until the desired important portion appears on the display device. Known portable communication devices also lack provision for automatically stopping the procession of messages when telephone numbers are being displayed.
Attempts have been made to make it possible to manually stop the procession of characters on the display device by inclusion of a freeze switch which, upon depression by a user, would stop the procession. An example of such a feature is shown in U.S. Pat. No. 3,976,995 entitled Precessing Display Pager, issued Aug. 24, 1976 to Sebestyen. However, such provision disadvantageously requires the user to depress the freeze button while the important portion of the message, such as a telephone number, is still viewable on the display. As a result, it is necessary that the user react quickly and/or the rate of procession be kept slow which can be annoying because most users are capable of reading words at a faster rate of procession. Another known method of displaying characters entails the automatic pausing of the procession of words, (i.e., groups of alphanumeric characters separated by the space character), when the word reaches the left edge or another preselected position on the display device. An example of a paging receiver with such feature is described in U.S. Pat. No. 4,660,032 entitled Radio Paging Receiver Operable on a Word-Scrolling Basis, issued Apr. 21, 1987 to Tsunoda. However, the radio paging receiver of Tsunoda disadvantageously pauses on all words, however long or short, and on all numeric sequences, however long or short.
More recently, a paging receiver that recognizes the difference between an alphabetic character and a numeric character within a message and that displays numeric characters a longer period of time than the period it displays alphabetic characters has been developed. An example of such a paging receiver is disclosed in U.S. Pat. No. 4,952,957 entitled Paging Receiver with Dynamically Allocated Display Rate, issued Aug. 28, 1990 to DeLuca, et al., and assigned to the assignee of the present invention. The paging receiver disclosed in DeLuca provides satisfactory performance under most, but not necessarily all operating circumstances. For example, such a paging receiver unnecessarily slows the procession of all numeric characters, including single characters and short numeric "words" that can easily be memorized, because DeLuca lacks provision for distinguishing long numeric words from short numeric words.
Known portable communication devices also lack provision for procession at a fast rate when short words are being displayed, and then smoothly slowing the procession rate when long words are being displayed. Attempts have been made to make it possible to slow the procession of characters on the display device in response to the length of words. For example, U.S. Pat. No. 3,938,139 entitled Miniature Display Communicator, issued Feb. 10, 1976 to Day automatically increases the time period of the viewing cycle of each word transferred to the display in proportion to word length. In the miniature display communicator of Day, although there is a procession of words, words are illuminated only while the words are stopped, and the term "viewing cycle" means the time period that a stationary word on the display is illuminated. In Day, the rate of procession does not change with word length; indeed, the rate of procession is not discernible because words are not illuminated during procession. Also known are alphanumeric products having means for a user to preselect the message procession speed; however, the procession speed in such products disadvantageously remains non-responsive to the content of a message.
Thus, what is necessary is an improved display device for use in a selective call receiver that recognizes telephone numbers and long words, and which automatically, selectively displays the telephone numbers and long words in manners that overcomes the deficiencies of the prior art.